Cellulose acylate films are used for various liquid crystal displays, as optical elements thereof, such as supports for optical compensation films, and protective films for polarizing plates.
In addition to an indoor use of the liquid crystal display, such as a TV use, a chance of the outdoor use thereof is increased, for example, use as a mobile device. As a result, development of a liquid crystal display is required, which is impervious to the use under the conditions of higher temperature and higher humidity than ever before. However, when the liquid crystal display is used under the conditions of higher temperature and higher humidity, there is a problem of deterioration of display performance due to occurrence of unevenness or lowering in polarization performance, each of which is caused by contraction of the polarizer. Further, in the liquid crystal display, a demand for durability in a wide array of uses and under extreme use condition has been increasing, and year after year a higher level of durability than before has been required. Further, more improvement in these performances has been required as a result of making a liquid crystal display thinner in recent years.
Patent Literature 1 describes that durability of the polarizer under the conditions of higher temperature and higher humidity can be improved, by a resin film (including a cellulose acylate film) containing an organic acid with acid dissociation constant of from 2 to 7 in a particular solvent. Further, Patent Literature 2 proposes to suppress retardation developing property and internal haze, by a chelating agent whose chelate constant (chelate stability constant) with Ca2+ ions is 2 or more.